1. Field of the Invention
The present invention relates to internal combustion engines and, more particularly, to a piston head having a top surface recess.
2. Prior Art
The small two-stroke engine has many desirable characteristics including: simplicity of construction, low cost of manufacturing, high power-to-weight ratios, high speed operational capability and, in many parts of the world, ease of maintenance with simple facilities. The prominent drawback of the simple two-stroke engine is the loss of a portion of the fresh unburned fuel charge from the cylinder during the scavenging process. This leads to poor fuel economy and high emission of unburned hydrocarbon, thus rendering the simple two-stroke engine incapable of compliance with increasingly stringent governmental pollution restrictions. This drawback can be relieved by separating the scavenging of the cylinder, with fresh air, from the charging of the cylinder, with fuel. This separation can be achieved by injecting the liquid fuel into the cylinder or more preferably by injecting the fuel charge by utilizing a pressurized air source, separate from the fresh air scavenge, to spray the fuel into the cylinder.
In accordance with one embodiment of the present invention, a method of controlling fuel injection flow in a cylinder of an internal combustion engine is provided comprising steps of providing a piston head of the engine with a combined flow redirector and holding bowl recess extending into a top side of the piston head; providing a fuel injection port in the cylinder in a bottom portion of a swept volume of the cylinder located above the top side of the piston head when the piston is at a bottom dead center position; injecting fuel from the injection port into the recess, wherein the step of injecting comprises; injecting the fuel at a first velocity when the engine is operating at a first speed, and injecting the fuel at a second faster velocity when the engine is operating at a second faster speed. The recess holds a substantial portion of the injected fuel when the fuel is injected at the first velocity which is then subsequently transported in the recess to a spark plug of the engine as the piston moves towards a top dead center position, and the recess redirects a substantial portion of the injected fuel out of the recess when the fuel is injected at the second faster velocity.
In accordance with one method of the present invention a method of controlling fuel injection flow in a cylinder of an internal combustion engine is provided comprising steps of providing a piston head of the engine with a combined flow redirector and holding bowl recess extending into a top side of the piston head; providing a fuel injection port in the cylinder in a bottom portion of a swept volume of the cylinder located above the top side of the piston head when the piston is at a bottom dead center position; injecting fuel from the injection port into the recess. The step of injecting comprises injecting the fuel at a first velocity when the engine is operating at a first speed, and injecting the fuel at a second faster velocity when the engine is operating at a second faster speed. The recess holds a substantial portion of the injected fuel when the fuel is injected at the first velocity which is then subsequently transported in the recess to a spark plug of the engine as the piston moves towards a top dead center position. The recess redirects a substantial portion of the injected fuel out of the recess when the fuel is injected at the second faster velocity.
In accordance with another method of the present invention a method of combusting fuel in a cylinder of an internal combustion engine is provided comprising steps of injecting fuel into the cylinder while a piston of the engine is proximate a bottom dead center position, the fuel being injected into a bowl recess in a top surface of the piston; transporting a substantial portion of the fuel, injected into the cylinder, by the bowl recess to a spark plug of the engine as the piston moves towards a top dead center position; and igniting the fuel by the spark plug as the piston approaches the top dead center position, wherein the substantial portion of the fuel stays in the bowl recess between injection of the fuel into the bowl recess and ignition of the fuel by the spark plug.
In accordance with one embodiment of the present invention, an internal combustion engine is provided comprising a cylinder, a piston movably mounted in the cylinder, and a fuel injection system for injecting fuel into the cylinder. The piston has a top surface with a combined flow redirection and holding bowl recess. The fuel injection system has an injection port located in a lateral side wall of the cylinder at a bottom section of a swept volume of the cylinder proximate the recess in the top surface of the piston for injecting fuel into the recess with a small space between the injection port and a receiving area of the recess when the piston is located proximate a bottom dead center position.